If you want to receive Sky TV, Freeview or video on a another TV in your house, the old fashioned way of doing this would require running a coax cable from one room to another. This is obviously hard work and means drilling holes in walls and having cables trailing.
The perfect alternative is a Wireless TV link. Basically the main transmitter sends pictures from your video, satellite or DVD player or set top box over the air to another TV elsewhere in the house which will be fitted with a receiver. All wireless TV links can transmit over short distances and even through walls, although if you're trying to transmit through several walls, or over a long distance, they may be less effective.